A forward and reverse collaborative design method and system for a symmetrical two-stage expansion nozzle

Abstract

The present invention discloses a forward and reverse collaborative design method and system for a symmetrical two-stage expansion nozzle. The nozzle is divided into a basic section and an extension section, aiming to improve the performance of the nozzle in a wide airspace and a wide speed range. The profile of the basic section is generated by an inverse design method based on wall pressure to adjust the shock wave position and shorten the negative thrust surface, thereby improving the thrust performance under low Mach number conditions. The profile of the extension section adopts a maximum thrust nozzle design method based on strong geometric constraints to meet the requirements of the integrated design of the rear body of a hypersonic aircraft. The steps include determining the wall pressure distribution of the basic section, calculating the influence domain, designing the wall profile of the basic section, calculating the initial value line of the extension section, calculating the initial expansion section of the extension section, designing the profile of the extension section, and regulating the nozzle performance. The advantage of the present invention is that it can improve the performance of the nozzle in a wide airspace and a wide speed range, thereby meeting the design requirements of the integrated rear body of a hypersonic aircraft.

Description

Technical Field

[0001] The present invention relates to the field of aerospace propulsion technology, and in particular to a forward and reverse collaborative design method and system for a symmetrical two-stage expansion nozzle. Background Art

[0002] The nozzle, a key component in scramjet engines, directly impacts thrust generation. Therefore, achieving high-performance nozzle design is a key technology for scramjet engines. Under wide flight conditions and speed ranges, the nozzle inevitably experiences expansion. Especially at low speeds, the nozzle experiences severe overexpansion, resulting in negative thrust. For example, when operating in the ejection mode of a rocket-based combined cycle engine, flow separation is prone to occur within the nozzle, resulting in negative thrust. To maintain thrust performance at low pressure drop ratios, the ejection rocket requires high flow rates. This increases fuel consumption during ejection mode, significantly impacting the vehicle's overall payload efficiency. Therefore, considering fuel economy and reducing the rocket's operating time, reducing negative nozzle thrust can significantly reduce the rocket's involvement in the process and improve overall vehicle performance.

[0003] The two-stage expansion nozzle is a lightweight altitude-compensating nozzle with a simple structure, capable of spontaneous mode switching without mechanical operation. Its expansion section is divided into a base section and an extension section profile. The two-stage expansion nozzle effectively utilizes the nozzle area ratio. At low altitude, the base section design enables the nozzle to effectively control the flow separation generated by nozzles with large area ratios. The base section maintains full flow, while the extension section is in a separated state. The shock wave position is controlled at the profile turning point. At this point, the expansion surface of the base section is the primary component affecting axial thrust performance. At high altitude, both the base and extension sections operate in a full flow state. At this point, the expansion surfaces of the base and extension sections are the primary components affecting axial thrust performance, achieving altitude compensation characteristics. In this context, it is found that research on the profile design of two-stage expansion nozzles is relatively mature, and nozzle shape has a significant impact on performance. Therefore, further research on the design methods of two-stage expansion nozzles is necessary. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a method and system for the collaborative forward and reverse design of a symmetrical, two-stage expansion nozzle. To improve nozzle performance across a wide range of airspace and speeds, the nozzle base section profile is generated using an inverse design method based on wall pressure. This modifies the shock wave position and shortens the nozzle's negative thrust surface, thereby improving nozzle thrust performance at low Mach numbers. The nozzle extension section profile utilizes a maximum thrust nozzle design method based on strong geometric constraints, meeting the requirements of a hypersonic vehicle's aft-body integrated design.

[0005] In order to achieve the above object of the invention, the technical solution adopted by the present invention is as follows:

[0006] A forward and reverse collaborative design method for a symmetrical two-stage expansion nozzle includes the following steps:

[0007] Step 1: Determine the wall pressure distribution of the base section of the two-stage expansion nozzle based on the upper wall pressure distribution of the fully geometrically constrained maximum thrust nozzle in a severely overexpanded state and the position of the shock wave in the nozzle;

[0008] Step 2: Based on the low pressure drop ratio working condition and the initial expansion section profile, the influence domain of the nozzle inlet and the initial expansion section is calculated using the rotating characteristic line method;

[0009] Step 3: Based on the pressure distribution on the base section wall, the influence domain of the nozzle base section and the profile of the base section wall are designed using the rotating characteristic line method and the controlled pressure inverse design method;

[0010] Step 4: Based on the high drop pressure ratio working condition, the last right characteristic line of the nozzle base section is calculated using the rotating characteristic line method. This right characteristic line is the initial value line of the nozzle extension section.

[0011] Step 5: To meet the requirements for hypersonic vehicle aft body integration, the length and height of the two-stage expansion nozzle are specified. The initial expansion section and the exit influence domain of the nozzle extension are obtained using the rotating characteristic line method, the maximum thrust theory, and the flow conservation iteration.

[0012] Step 6: Change the pressure distribution in the nozzle base section to control the shock wave position in the two-stage expansion nozzle, and then actively adjust the nozzle performance to complete the symmetrical two-stage expansion nozzle design.

[0013] Furthermore, the step 1 includes the following steps:

[0014] Step 11: The nozzle obtained by the maximum thrust nozzle design method with full geometric constraints (length and height constraints) is the basic nozzle;

[0015] Step 12: Determine the initial length L of the nozzle base section based on the upper wall pressure distribution of the basic nozzle in a severely over-expanded state and the shock wave position in the basic nozzle. ini and the pressure p at the end of the initial wall of the foundation segment ini , the initial wall pressure distribution p(x) of the base section is obtained by polynomial fitting ini ;

[0016] Step 13: Introduce the position control factor n to control the length L of the nozzle base section b ; Introduce the pressure control factor β to control the pressure p at the end of the nozzle base section wall b, determine the pressure distribution p(x) on the nozzle base section; the position control factor n and the pressure control factor β are defined as follows:

[0017]

[0018] Furthermore, in step 2, the initial expansion section of the nozzle base section is an arc.

[0019] Furthermore, the step 5 includes the following steps:

[0020] Step 51, the first-order derivative of the starting point of the initial expansion section of the nozzle extension section is the same as the first-order derivative of the end point of the basic section;

[0021] Step 52 , based on the overall dimensional constraints of the two-stage expansion nozzle, i.e., length and height, the extension section is dimensionally constrained;

[0022] Step 53, introduce the design point Ma J , control the expansion degree of the initial expansion section of the nozzle extension section so that the Mach number at its end point is equal to Mach J , using the method of rotating characteristic lines, the influence domain of the initial expansion section of the extension section and the final characteristic line JK emitted by the expansion surface are obtained;

[0023] In step 54, point M is an arbitrary point on JK. Maximum thrust theory and flow conservation are used to determine the flow parameters and position information along the left-moving characteristic line MN originating from point M. By moving point M to obtain nozzles of varying lengths, the desired left-moving characteristic line MN is obtained when the length constraint is satisfied.

[0024] Step 55: Since the nozzle may not meet the altitude constraint, it is necessary to change the design Mach number Ma through an iterative algorithm. J Iterate steps 53 and 54 until the nozzle satisfies both the length and height constraints. The aerodynamic parameters on the last left characteristic line need to satisfy the following equations:

[0025]

[0026] ρV 2 sin 2 θtanα=C2

[0027] Where ρ is the fluid density, V is the fluid velocity, θ is the flow angle, α is the Mach angle, and C1 and C2 are constants calculated from the physical parameters of the starting point M of the last left-hand characteristic line of the nozzle and the above formula.

[0028] Furthermore, in step 6, the pressure distribution of the nozzle base section is changed by adjusting the position control factor n and the pressure control factor β in step 1.

[0029] Furthermore, the rotational characteristic line method includes the following characteristic line equation:

[0030]

[0031] where x and y represent two-dimensional Cartesian coordinates, and λ + Left characteristic line C + The slope of λ is the right characteristic line C - , λ0 is the slope of the streamline C0, u and v represent the velocity components along the x and y directions, respectively.

[0032] Furthermore, the rotational characteristic line method also includes the following compatibility equation:

[0033] ρVdV+dP=0

[0034] dP-a 2 dρ=0

[0035]

[0036] Where Ma is the Mach number, P is the static pressure, a is the speed of sound, ρ is the fluid density, V is the fluid velocity value, θ is the flow angle, α is the Mach angle, and δ is the parameter of symmetric flow. If the flow is symmetric, then δ = 1.

[0037] The present invention also discloses a forward and reverse collaborative design system for a symmetrical two-stage expansion nozzle. The system can be used to implement the forward and reverse collaborative design method for the symmetrical two-stage expansion nozzle, specifically comprising:

[0038] Base section wall pressure distribution determination module: Based on the upper wall pressure distribution of the maximum thrust nozzle with full geometric constraints in a severely overexpanded state and the position of the shock wave in the nozzle, the wall pressure distribution of the base section of the two-stage expansion nozzle is determined.

[0039] Initial expansion section influence domain calculation module: Based on the low drop pressure ratio working condition and the initial expansion section profile, the influence domain of the nozzle inlet and the initial expansion section is calculated using the rotating characteristic line method.

[0040] Base section influence domain and wall profile design module: Based on the pressure distribution on the base section wall, the influence domain and wall profile of the nozzle base section are designed using the rotating characteristic line method and the controlled pressure inverse design method.

[0041] Initial value line calculation module of the nozzle extension section: According to the high drop pressure ratio working condition, the rotating characteristic line method is used to calculate the last right characteristic line of the nozzle base section. This right characteristic line is the initial value line of the nozzle extension section.

[0042] Nozzle Extension Design Module: Specifies the length and height dimensions of the two-stage expansion nozzle, and uses the rotating characteristic curve method, maximum thrust theory, and flow conservation iteration to obtain the initial expansion section and exit influence domain of the nozzle extension.

[0043] Nozzle performance control module: By changing the pressure distribution in the base section of the nozzle, the shock wave position in the two-stage expansion nozzle is controlled, thereby actively regulating the nozzle performance.

[0044] Result output module: summarizes and outputs the results of each design stage and generates a final design report.

[0045] The output content includes: base section wall pressure distribution, initial expansion section influence domain, base section influence domain, wall profile, initial value line of nozzle extension section, initial expansion section, outlet influence domain, nozzle performance control parameters and effects.

[0046] The present invention also discloses a computer device, including a memory, a processor, and a computer program stored in the memory and runnable on the processor. When the processor executes the program, the above-mentioned symmetrical-two-stage expansion nozzle forward and reverse collaborative design method is implemented.

[0047] The present invention also discloses a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the above-mentioned symmetrical-two-stage expansion nozzle forward and reverse collaborative design method is realized.

[0048] Compared with the prior art, the advantages of the present invention are:

[0049] 1. Altitude Compensation: The design method fully utilizes the nozzle's effective area ratio, enabling it to maintain high performance across various flight conditions. Under low-speed overexpansion conditions, an inverse design method is used to adjust the wall pressure distribution and base section profile, effectively controlling the base section length and pressure distribution to optimize the nozzle expansion.

[0050] 2. Reduce negative thrust: For low-speed conditions, by controlling the wall pressure, the nozzle expansion degree is made to present a "fast at the front and slow at the back" shape, which advances the shock wave position and shortens the nozzle negative thrust surface, thereby reducing negative thrust.

[0051] 3. Optimize thrust performance: Under high-speed flight conditions, a maximum thrust nozzle design method based on strong geometric constraints is adopted to optimize the thrust performance of the nozzle under geometric constraints to meet the requirements of the integrated design of the rear body of the hypersonic aircraft.

[0052] 4. Flexible control: By changing the pressure distribution in the base section, the shock wave position in the two-stage expansion nozzle can be actively controlled, thereby precisely controlling the nozzle performance.

[0053] 5. Front and rear collaborative design: Combining the characteristic line design of the front and rear sections to achieve collaborative optimization of the front and rear sections of the nozzle, ensuring the optimal overall performance of the nozzle under different flight conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 1. It is a schematic structural diagram of the profiles of the base section and the extension section of a two-stage expansion nozzle determined in the forward and reverse collaborative design method of a symmetrical two-stage expansion nozzle according to an embodiment of the present invention;

[0055] Figure 2 Schematic diagram of the profile and wall pressure of the nozzle base section designed after the position control factor n and the pressure control factor β are introduced into the embodiment of the present invention.

[0056] Figure 3 This is a comparison diagram of the pressure distribution of the nozzle profile of the wall pressure distribution inverse design according to an embodiment of the present invention obtained by CFD inviscid calculation and the given wall pressure distribution;

[0057] Figure 4 This is a comparison diagram of the wall pressure distribution at low and high speeds for a symmetrical two-stage expansion nozzle obtained by designing the nozzle extension profile using a maximum thrust nozzle design method based on strong geometric constraints and a maximum thrust nozzle based on full geometric constraints;

[0058] Among them, AB is the nozzle inlet, AF is the wall profile of the nozzle base section, FG is the last characteristic line from the nozzle base section, FJ is the initial expansion section of the nozzle extension section, FJN is the wall profile of the nozzle extension section, JK is the last right-running characteristic line from the initial expansion section of the extension section, M is the intersection of the characteristic lines, and MN is the left-running characteristic line passing through the intersection point.

[0059] F is the end point of the nozzle base section, S' is the shock wave position of the basic nozzle in a severely over-expanded state, S is any point before the shock wave position of the basic nozzle, and its flow parameters and position parameters are the initial values ​​of point F in the present invention. The pressure at point S is recorded as p ini The projection distance from the nozzle inlet to point S in the x direction is recorded as L ini ;

[0060] ①—influence domain of nozzle inlet, ②—influence domain of initial expansion section, ③—influence domain of base section, ④—influence domain of initial expansion section, ⑤—influence domain of nozzle outlet.

[0061] 1, 2, 3, 4—the end point F of the basic section, where points 1 and 3 represent the case where the pressure control factor is 1, and the position control factors are 0.5 and 1.5 respectively. It can be seen that when n>1, the expansion rate of the nozzle basic section becomes slower than that of the basic nozzle, and the length becomes longer. When n<1, the opposite is true. Points 2 and 4 represent the case where the position control factor is 1, and the pressure control factors are 1.3 and 0.7 respectively. It can be seen that when β>1, the expansion rate of the nozzle basic section becomes faster than that of the basic nozzle, and the height becomes higher. When β<1, the opposite is true. DETAILED DESCRIPTION

[0062] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.

[0063] Combine Figure 1 As shown, the present invention discloses a forward and reverse collaborative design method for a symmetrical two-stage expansion nozzle, comprising the following steps:

[0064] Step 1: Based on the upper wall pressure distribution of the fully geometrically constrained maximum thrust nozzle in a severely overexpanded state and the position of the shock wave in the nozzle, determine the wall pressure distribution of the base section AF of the two-stage expansion nozzle;

[0065] Step 2: Based on the low pressure drop ratio working condition and the initial expansion section profile, the influence domains of the nozzle inlet and the initial expansion section are calculated using the rotating characteristic line method, ① and ②;

[0066] Step 3: Based on the pressure distribution on the base section wall, the nozzle base section influence domain ③ and the base section wall profile AF are designed using the rotating characteristic line method and the controlled pressure inverse design method.

[0067] The controlled pressure inverse design method is a design method based on wall pressure distribution, which aims to adjust the geometry of the nozzle through the wall pressure distribution so that the pressure distribution inside the nozzle meets the design requirements.

[0068] Step 4: Based on the high drop pressure ratio working condition, the last right characteristic line FG of the nozzle base section is calculated using the rotating characteristic line method. This right characteristic line is the initial value line of the nozzle extension section.

[0069] Step 5: To meet the requirements of hypersonic vehicle aft body integration, the length and height of the two-stage expansion nozzle are specified. The initial expansion section FJ, the initial expansion section influence domain ④, and the outlet influence domain ⑤ of the nozzle extension section are obtained using the rotating characteristic line method, the maximum thrust theory, and the flow conservation iteration.

[0070] Step 6: Change the AF pressure distribution in the nozzle base section to control the shock wave position in the two-stage expansion nozzle, thereby actively regulating the nozzle performance and completing the symmetrical two-stage expansion nozzle design.

[0071] In the present invention, the rotational characteristic line method used includes the following characteristic line equations:

[0072]

[0073]

[0074] where x and y represent two-dimensional Cartesian coordinates, and λ + Left characteristic line C + The slope, λ - Right characteristic line C - , λ0 is the slope of the streamline C0, u and v represent the velocity components along the x and y directions, respectively.

[0075] In the present invention, the rotation characteristic line method also includes the following compatibility equation:

[0076] ρVdV+dP=0

[0077] dP-a 2 dρ=0

[0078]

[0079] Wherein, Ma is the Mach number, P is the static pressure, a is the speed of sound, the subscript + represents the left characteristic line, and the subscript - represents the right characteristic line. The nozzle of the present invention has a symmetrical flow, δ=1, and if it is a planar flow, δ=0.

[0080] In the present invention, the extended section profile is calculated using the rotational characteristic line method and the iterative method. The aerodynamic parameters on the last left characteristic line need to satisfy the following equation, which is obtained using the maximum thrust theory:

[0081]

[0082] ρV 2 sin 2 θtanα=C2

[0083] Where ρ is the fluid density, V is the fluid velocity, θ is the flow angle, α is the Mach angle, and C1 and C2 are constants calculated from the physical parameters of the starting point M of the last left-hand characteristic line of the nozzle and the above formula.

[0084] Combine Figure 2 In the present invention, the wall pressure distribution of the base section AF of the two-stage expansion nozzle is determined based on the upper wall pressure distribution of the fully geometrically constrained maximum thrust nozzle in a severely overexpanded state and the position of the shock wave in the nozzle. The specific steps are as follows:

[0085] Step 1): Under low drop pressure ratio, the upper wall pressure distribution of the basic nozzle in a severe overexpansion state and the shock wave position S' in the nozzle are obtained by CFD inviscid calculation. An arbitrary point on the wall before the shock wave position in the basic nozzle is selected as the initial point S;

[0086] Step 2): The flow parameters and position information of point S are used as the initial parameters of point F to determine the initial length L of the nozzle base section AF in the present invention. ini and the pressure p at point F at the end of the initial wall of the foundation segment ini Based on the wall pressure distribution before point S of the basic nozzle, the initial wall pressure distribution p(x) of the basic section is obtained by polynomial fitting. ini ;

[0087] Step 3): Further, introduce the position control factor n to control the length L of the nozzle base section b ; Introduce the pressure control factor β to control the pressure p at the end of the nozzle base section wall b , determine the pressure distribution p(x) on the nozzle base section; the position control factor n and the pressure control factor β are defined as follows:

[0088]

[0089] The design method of this invention is a collaborative forward-inverse design approach developed based on maximum thrust theory and can be applied to the tail nozzle design of scramjets and combined cycle engines. For wide-airspace, wide-speed range nozzles, inverse design of the nozzle base section profile based on wall pressure distribution can control the base section length and wall pressure, thereby controlling the shock wave position, thereby shortening the nozzle's negative thrust surface and reducing the nozzle's negative thrust. A maximum thrust nozzle design method based on strong geometric constraints optimizes the nozzle's thrust performance within these geometric constraints, meeting the design objectives of an integrated hypersonic vehicle aft body.

[0090] To better illustrate the present invention and facilitate understanding of the technical solutions of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0091] Table 1 shows the low-speed operating conditions of the nozzle, and Table 2 shows the design operating conditions of the nozzle.

[0092] Table 1

[0093]

[0094] Table 2

[0095]

[0096] Figure 4The following is a comparison of the wall pressure distribution of the symmetrical two-stage expansion nozzle designed by the present invention and the basic nozzle under low-speed and high-speed flight conditions, where n = 1, β = 1 represents the wall pressure of the basic nozzle; the nozzle base section length is initially set to 50 mm, and n = 0.8, β = 1 are introduced to obtain a new base section wall pressure distribution, and a two-stage expansion nozzle is designed. Its wall pressure distribution is obtained by numerical simulation. Table 3 is the nozzle performance comparison data of the nozzle designed by the present invention and the basic nozzle design. The basic nozzle is designed based on the maximum thrust nozzle design method with full geometric constraints. The main steps are as follows: (1) According to the nozzle inlet parameter distribution and the overall geometric constraints, the parameters on the last left characteristic line of the nozzle are determined by the rotation characteristic line method, interpolation method and iteration method; (2) According to the flow conservation law, the nozzle profile is further calculated using the rotation characteristic line method.

[0097] Table 3 is the performance comparison data of the nozzle designed by the present invention and the nozzle designed based on the maximum thrust nozzle with full geometric constraints.

[0098] Table 3

[0099]

[0100] The nozzle designed by the present invention has a thrust performance improved by 7.86% compared with the maximum thrust nozzle with full geometric constraints under the typical over-expansion state of low-speed flight, and the shock wave position is moved forward by 43 mm compared with the shock wave position of the original nozzle. However, the thrust performance is only reduced by 0.75% under the typical state of high-speed flight, which verifies the correctness of the design concept and provides a theoretical basis for the exhaust system of hypersonic aircraft.

[0101] In yet another embodiment of the present invention, a forward-reverse collaborative design system for a symmetrical two-stage expansion nozzle is provided. The system can be used to implement the forward-reverse collaborative design method for a symmetrical two-stage expansion nozzle, specifically comprising:

[0102] Base section wall pressure distribution determination module: Based on the upper wall pressure distribution of the maximum thrust nozzle with full geometric constraints in a severely overexpanded state and the position of the shock wave in the nozzle, the wall pressure distribution of the base section of the two-stage expansion nozzle is determined.

[0103] Initial expansion section influence domain calculation module: Based on the low drop pressure ratio working condition and the initial expansion section profile, the influence domain of the nozzle inlet and the initial expansion section is calculated using the rotating characteristic line method.

[0104] Base section influence domain and wall profile design module: Based on the pressure distribution on the base section wall, the influence domain and wall profile of the nozzle base section are designed using the rotating characteristic line method and the controlled pressure inverse design method.

[0105] Initial value line calculation module of the extension section: According to the high drop pressure ratio working condition, the rotating characteristic line method is used to calculate the last right characteristic line of the nozzle base section. This right characteristic line is the initial value line of the nozzle extension section.

[0106] Nozzle Extension Design Module: Specifies the length and height dimensions of the two-stage expansion nozzle, and uses the rotating characteristic curve method, maximum thrust theory, and flow conservation iteration to obtain the initial expansion section and exit influence domain of the nozzle extension.

[0107] Nozzle performance control module: By changing the pressure distribution in the base section of the nozzle, the shock wave position in the two-stage expansion nozzle is controlled, thereby actively regulating the nozzle performance.

[0108] Result output module: summarizes and outputs the results of each design stage and generates a final design report.

[0109] The output content includes: base section wall pressure distribution, initial expansion section influence domain, base section influence domain, wall profile, extension section initial value line, initial expansion section, outlet influence domain, nozzle performance control parameters and effects.

[0110] In another embodiment of the present invention, a terminal device is provided, comprising a processor and a memory, wherein the memory is configured to store a computer program, wherein the computer program includes program instructions, and the processor is configured to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may be another general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc., and is the computing core and control core of the terminal, and is adapted to implement one or more instructions, specifically, to load and execute one or more instructions to implement a corresponding method flow or corresponding function. The processor described in this embodiment of the present invention can be used to operate the forward and reverse collaborative design method for a symmetrical two-stage expansion nozzle.

[0111] In another embodiment of the present invention, the present invention further provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a terminal device for storing programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and, of course, the extended storage medium supported by the terminal device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space. These instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory.

[0112] One or more instructions stored in a computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the forward and reverse collaborative design method of a symmetrical-two-stage expansion nozzle in the above embodiment; one or more instructions in the computer-readable storage medium are loaded and executed by the processor.

[0113] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0114] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0115] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0116] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0117] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the implementation methods of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the present invention.

Claims

1. A symmetrical two-stage expansion nozzle forward and reverse collaborative design method, characterized in that: The following steps are involved: Step 1: Determine the wall pressure distribution of the base section of the two-stage expansion nozzle based on the upper wall pressure distribution of the fully geometrically constrained maximum thrust nozzle in a severely overexpanded state and the position of the shock wave in the nozzle; The step 1 comprises the following steps: Step 11: The nozzle obtained by the maximum thrust nozzle design method with full geometric constraints is used as the basic nozzle; Step 12: Based on the upper wall pressure distribution of the basic nozzle in a severely over-expanded state and the shock wave position in the basic nozzle, an initial wall point is selected before the shock wave position of the basic nozzle to determine the initial length L of the nozzle base section. ini and the pressure p at the end of the initial wall of the foundation segment ini , the initial wall pressure distribution p(x) of the base section is obtained by polynomial fitting ini ; Step 13: Introduce the position control factor n to control the length L of the nozzle base section b ; Introduce the pressure control factor β to control the pressure p at the end of the nozzle base section wall b , determine the pressure distribution p(x) on the nozzle base section; the position control factor n and the pressure control factor β are defined as follows: Step 2: Based on the low pressure drop ratio working condition and the initial expansion section profile, the influence domain of the nozzle inlet and the initial expansion section is calculated using the rotating characteristic line method; Step 3: Based on the pressure distribution on the base section wall, the influence domain of the nozzle base section and the profile of the base section wall are designed using the rotating characteristic line method and the controlled pressure inverse design method; Step 4: Based on the high drop pressure ratio working condition, the last right characteristic line of the nozzle base section is calculated using the rotating characteristic line method. This right characteristic line is the initial value line of the nozzle extension section. Step 5: To meet the requirements for hypersonic vehicle aft body integration, the length and height of the two-stage expansion nozzle are specified. The initial expansion section and the exit influence domain of the nozzle extension are obtained using the rotating characteristic line method, the maximum thrust theory, and the flow conservation iteration. Step 6: Change the pressure distribution in the nozzle base section to control the shock wave position in the two-stage expansion nozzle, and then actively adjust the nozzle performance to complete the symmetrical two-stage expansion nozzle design.

2. The forward and reverse collaborative design method for a symmetrical two-stage expansion nozzle according to claim 1 is characterized in that: In step 2, the initial expansion section of the nozzle base section is an arc.

3. The forward and reverse collaborative design method for a symmetrical two-stage expansion nozzle according to claim 2 is characterized in that: The step 5 comprises the following steps: Step 51, the first-order derivative of the starting point of the initial expansion section of the nozzle extension section is the same as the first-order derivative of the end point of the basic section; Step 52 , based on the overall dimensional constraints of the two-stage expansion nozzle, i.e., length and height, the extension section is dimensionally constrained; Step 53, introduce the design point Ma J , control the expansion degree of the initial expansion section of the nozzle extension section so that the Mach number at its end point is equal to Mach J , using the method of rotating characteristic lines, the influence domain of the initial expansion section of the extension section and the final characteristic line JK emitted by the expansion surface are obtained; Step 54: Point M is an arbitrary point on JK. The maximum thrust theory and flow conservation are used to determine the flow parameters and position information along the left-moving characteristic line MN emitted from point M. By moving point M to obtain nozzles of different lengths, the desired left-moving characteristic line MN can be obtained when the length constraint is met. Step 55: Since the nozzle may not meet the altitude constraint, it is necessary to change the design Mach number Ma through an iterative algorithm. J Iterate steps 53 and 54 until the nozzle satisfies both the length and height constraints. The aerodynamic parameters on the final left characteristic line need to satisfy the following equations: ρV 2 sin 2 θtanα=C2 Where ρ is the fluid density, V is the fluid velocity, θ is the flow angle, α is the Mach angle, and C1 and C2 are constants calculated from the physical parameters of the starting point M of the last left-hand characteristic line of the nozzle and the above formula.

4. The forward and reverse collaborative design method for a symmetrical two-stage expansion nozzle according to claim 1 is characterized in that: In step 6, the pressure distribution of the nozzle base section is changed by adjusting the position control factor n and the pressure control factor β in step 1.

5. The forward and reverse collaborative design method for a symmetrical two-stage expansion nozzle according to claim 1 is characterized in that: The rotational characteristic line method includes the following characteristic line equations: where x and y represent two-dimensional Cartesian coordinates, and λ + Left characteristic line C + The slope, λ - Right characteristic line C - , λ0 is the slope of the streamline C0, u and v represent the velocity components along the x and y directions, respectively.

6. The forward and reverse collaborative design method for a symmetrical two-stage expansion nozzle according to claim 5 is characterized by: The rotational characteristic line method also includes the following compatibility equation: ρVdV+dP=0 dP-a 2 dρ=0 Where Ma is the Mach number, P is the static pressure, a is the speed of sound, ρ is the fluid density, V is the fluid velocity value, θ is the flow angle, α is the Mach angle, and δ is the parameter of symmetric flow. If the flow is symmetric, then δ = 1.

7. A symmetrical two-stage expansion nozzle forward and reverse collaborative design system, characterized by: The system can be used to implement the forward and reverse collaborative design method of a symmetrical two-stage expansion nozzle according to any one of claims 1 to 6, specifically including: Base section wall pressure distribution determination module: Based on the upper wall pressure distribution of the fully geometrically constrained maximum thrust nozzle in a severely overexpanded state and the location of the shock wave in the nozzle, the wall pressure distribution of the base section of the two-stage expansion nozzle is determined; Initial expansion section influence domain calculation module: Based on the low drop pressure ratio working condition and the initial expansion section profile, the influence domain of the nozzle inlet and the initial expansion section is calculated using the rotating characteristic line method; Base section influence domain and wall profile design module: Based on the pressure distribution on the base section wall, the influence domain and wall profile of the nozzle base section are designed using the rotating characteristic line method and the controlled pressure inverse design method; The initial value line calculation module of the nozzle extension section: Based on the high drop pressure ratio working condition, the rotating characteristic line method is used to calculate the last right characteristic line of the nozzle base section. This right characteristic line is the initial value line of the nozzle extension section. Nozzle Extension Design Module: Specifies the length and height dimensions of the two-stage expansion nozzle, and uses the swirling characteristic curve method, maximum thrust theory, and flow conservation iteration to obtain the initial expansion section and exit influence domain of the nozzle extension. Nozzle performance control module: By changing the pressure distribution in the nozzle base section, the shock wave position in the two-stage expansion nozzle is controlled, thereby actively regulating the nozzle performance; Result output module: summarizes and outputs the results of each design stage and generates the final design report; The output content includes: base section wall pressure distribution, initial expansion section influence domain, base section influence domain, wall profile, initial value line of nozzle extension section, initial expansion section, outlet influence domain, nozzle performance control parameters and effects.

8. A computer device, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the forward and reverse collaborative design method for a symmetrical two-stage expansion nozzle as claimed in one of claims 1 to 6 is implemented.

9. A computer-readable storage medium, characterized in that: A computer program is stored thereon, which, when executed by a processor, implements the forward and reverse collaborative design method of a symmetrical two-stage expansion nozzle as described in one of claims 1 to 6.

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